This invention relates to a drive mechanism for raising and lowering a roll-up door.
Roll-up doors are used as garage doors and as doors for vans and trucks.
A drive mechanism for raising and lowering a roll-up door is disclosed in U.S. Pat. No. 4,191,237 Voege dated Mar. 4, 1980. In this mechanism small diameter cables are wound onto winding drums. In accordance with conventional practice, the winding drums will be proportioned to permit the cable to be fully wound onto the drum without overlapping such that the wind in speed and pay out speed of the two cable systems are identical. While this mechanism does incorporate a clutch, the clutch is provided to permit the drive to slip in the event that the door strikes an obstruction when it is being driven to the open position or to the closed position.